Secondary batteries that are an example of electrochemical devices are in great demand in various fields such as power sources for portable electric equipment such as cell phones and smartphones, digital cameras, and notebook personal computers, and power sources (electric power storage equipment) for vehicles and households. Among the secondary batteries, lithium ion secondary batteries being an example of non-aqueous electrolyte secondary batteries that can be repeatedly charged/discharged have a high energy density, a light weight and excellent charging/discharging cycle characteristics, and are energy accumulation devices indispensable to daily life.
In such a non-aqueous electrolyte secondary battery, an electrode laminate configured by alternately laminating two types of electrodes (positive electrode and negative electrode) with a separator interposed therebetween is housed in an outer container, the electrode of the electrode laminate is connected to an electrode terminal (electrode lead), and the electrode terminal extends to the outside of the outer container.
The secondary battery is required to have different characteristics depending on devices using the secondary battery and use environments thereof, but improving the energy density per unit volume is necessary for use in various applications. Thus, flexible container made of a flexible film whose shape is highly flexible instead of a metal can whose shape is highly limited has been selected for the outer container of the non-aqueous electrolyte secondary battery. The flexible film is typically a laminate film in which resin layers are laminated on both surfaces of a metal foil. The outer container made of the flexible film can be closely in contact with an outer surface of the electrode laminate almost without gap, thereby making it possible to improve the energy density per unit volume and to achieve higher volume efficiency by having a thinner design. A secondary battery (film-packaged battery) having such an outer container made of the flexible film is disclosed in Patent Documents 1 to 2.
In a configuration disclosed in Patent Document 2, a support tab (protection lead) is disposed on an electrode tab that is a part of an electrode superposed on an electrode terminal (electrode lead). The electrode tab, the support tab, and the electrode terminal are joined together with the electrode tab sandwiched between the support tab and the electrode terminal. Providing the support tab enables reliability of the connection between the electrode tab and the electrode terminal to be improved, and enables preventing the electrode tab and electrode terminal from being damaged when they are joined.